One type of drill bit employed for very abrasive drilling, such as hard sandstone, is known as a diamond-impregnated bit. Typically, this bit has a solid head or crown that is cast in a mold. The crown is attached to a steel shank that has a threaded end for attachment to the drill string. The crown may have a variety of configurations and generally includes post and blade-like members formed in the mold. Channels separate the blades for drilling fluid flow.
One type of manufacturing method for such a bit is known as a high-temperature, long-cycle infiltrating process. A mold is constructed in the shape of the crown of the bit. Diamond particles or grit and a matrix material are mixed and distributed into the mold. The diamond particles in one prior art process have a tungsten coating. One method for coating the diamond particles with tungsten in the prior art technique is a chemical vapor deposition (CVD) process. The matrix material includes a binder metal, typically a copper alloy, and hard abrasive particles such as tungsten carbide.
The matrix material and tungsten-coated diamond particles are heated in the mold for a time and temperature sufficient for the matrix binder metal to melt and infiltrate through the hard particles and diamond particles. After cooling, the binder bonds the diamonds and the hard abrasive particles. While this method and the resulting bit work well, the diamond particles have a tendency to agglomerate together, leaving a greater density of diamonds in some areas than in other areas. In some cases, the diamonds may be touching each other rather than being uniformly dispersed, as desired.